1. Field of the Invention
Aspects of the present invention relate to a method of manufacturing a flat panel display device, and more particularly, to a method of manufacturing a flat panel display device sealed with a glass sealing material.
2. Description of the Related Art
In general, flat panel display devices such as organic light emitting display devices or thin film transistor-liquid crystal displays (TFT-LCDs) can be manufactured to have a thin and flexible structure. Because of these useful properties, research into flat panel display devices is being actively performed.
Typically, organic light emitting display devices may be degraded by humidity. Accordingly, there is a need for a sealing structure that prevents the permeation of humidity.
Conventionally, a metal can or glass substrate, which is a sealing member, is formed into a cap-shaped structure having grooves. Then, the grooves are filled with desiccant powder to absorb humidity. Alternatively, a desiccant film may be attached to the grooves by using a double-sided tape in order to absorb humidity. Then, the sealing member and a substrate, which include light emitting devices, are combined with each other and sealed with an ultraviolet (UV) hardening organic sealant or thermal hardening organic sealant.
Organic sealants for combining the sealing member and the substrate are susceptible to pressure. In addition, the humidity-resistance characteristics of organic sealants quickly decrease over time, and the sealing effect is decreases.
Due to these and/or other problems, a glass sealing material has recently been used instead of organic sealants to obtain excellent pressure-resistance characteristics and sealing characteristics. A laser beam is used to melt the glass sealing material.
US Patent Application No. 2007/0128967 discloses a sealing method using a glass sealing material and using a laser beam to melt the glass sealing material.
In the disclosed method, a plurality of emission devices are interposed between a pair of mother glasses that face each other. Each emission device is then completely surrounded by a closed loop structure formed of a glass sealing material, and then a laser beam is irradiated to the closed loop structure to melt the glass sealing material.
Since the laser beam is irradiated to the glass sealing material along the closed loop structure surrounding each emission device, the irradiation track that the laser beam travels may have the same shape as that of the closed loop structure that surrounds each emission device. Accordingly, the laser beam forms the same number of closed loop structures as the number of emission devices.
In this method, the cut surfaces of the mother glasses may have defects due to thermal stress generated during laser beam irradiation.
When the glass sealing material is melted by the laser beam to combine the mother glasses, a cycle of increasing and decreasing of the temperature is repeated when the glass sealing material is melted and cooled. As a result, various thermal impacts are applied to the mother glasses, and thus, non-uniform stresses occur in the mother glasses. Due to non-uniform stresses, it may be difficult to cut the mother glasses accurately, and cut sides thereof may have protrusions. In addition, portions of the mother glasses corresponding to part of the emission devices may expand and form visible Newton-ring structures.
Furthermore, whenever laser beams are irradiated onto neighboring emission devices, more stress variations occur in the mother glasses.